KR20200124689A - Mass spectrometer method and apparatus for monitoring for TATP - Google Patents

Abstract

A method and apparatus for monitoring an air sample for the presence of explosive TATP is disclosed. A preferred approach uses proton-transfer reaction mass spectrometry PTR-MS. The system can be operated continuously in real time or near real time. A delivery tube of specific dimensions and material is used to introduce the sample into the ionization chamber, which in turn generates ions, which are transferred to the mass spectrometer to determine the m/z value. The system can use multiple ionization chambers to reduce the amount of false negative identifiers. Multiple inlet ion funnels can be used to combine ions from each ionization chamber. Chemical ionization can be used. A verification module can be used to reduce the amount of false positive identifiers.

Description

Mass spectrometer method and apparatus for monitoring for TATP

The present invention discloses a method and apparatus for continuously sensing TATP in real time by drawing ambient air through a pipe to an analysis standoff device. The invention is based in particular on the use of specific electronic conditions for chemical ionization techniques in conjunction with mass spectrometers.

Explosive detection has been a long-standing concern of the military and, more recently, security agencies, and has become increasingly important in connection with attacks after the 9/11 (Makinen M., et al. (2011) Ion Spectrometric detection technologies for ultra-traces of explosives: a review.Mass Spectrom. Rev. 30, 940-973).

In recent years, the non-peaceful use of explosives and their widespread application to malicious attacks has increased substantially, raising the threat of terrorist activity worldwide. Information on the synthesis of toxic and explosive substances is readily available in public information today, and raw materials for the synthesis of explosives are commercially available. This not only increases the risk of explosive-based attacks, but also increases the psychological impact on people. Meanwhile, due to the research on explosives, a variety of potential substances causing problems in detection devices are expanding (Internet site: Triacetone Tripperoxide (TATP)-GlobalSecurity.org www.globalsecurity.org> Military> Systems> Munitions> Introduction> Explosives July 7, 2011 (accessed Dec 29, 2016)).

Due to the wide range of energetic substances and the many differences in their physical properties, some sensing devices only detect certain types of explosives and others do not. For example, many sensing devices easily detect conventional explosives made of organic nitro and nitrate compounds, but not explosives made of inorganic nitrates or non-nitrogen compounds. In particular, many nitrogen-based sensing devices include ANFO (ammonium nitrate in fuel oil), black powder ("gun powder" formed of potassium nitrate, sulfur and charcoal), TATP (triacetone tripperoxide) and HMTD ( It does not detect explosives such as hexamethylene tripperoxide diamine). Consequently, these explosives are sometimes referred to as "transparent".

In the review literature published in 2016 on the technology currently available for explosive detection, the following was noted (Giannoukos S., et al. (2016) Chemical Sniffing Instrumentation for Security Applications. Chem. Rev. 116, 8146) -8172]): "The demand for accurate chemical analysis in real-time or near real-time requires more and more technology that works'in the field'. Chemical analysis in the field eliminates sample transfer/storage costs and remote laboratories Minimizes the risk of sample contamination during shipment to the site In addition to time and cost savings, on-site analysis enables rapid problem resolution, decision making, and streamlining operations The existing major challenges during field work are (a) the background chemical environment Is the complexity of, (b) potential device drawbacks/limitations, and (c) the complexity of the properties of the target sample compound."

According to the laws of physics, the concentration of gases emitted from a point source decreases as the cube of the distance from the source and the area, which is affected by the direction and speed of the wind. In terms of identifying sources of illegal substances, this means that sampling should take place as close to the point source as possible. However, in order to reduce the risk of damage or loss of inventory and personnel, the analysis should be performed as far away as possible.

For field and laboratory settings, most prior art explosive detection methods for trace level detection are described in Mayew C., et al. (2010) Applications of proton transfer reaction time-of-flight mass spectrometry for the sensitive and rapid real-time detection of solid high explosives. Int. J. Mass Spec. 289, 58-63], requires close contact between the sample and the assay device and/or pre-concentration of the sample.

According to the authors of the above reference, it is stated that a heated injection port had to be used to detect parent ions and a cooled spot had to be avoided. Moreover, it has been observed that traces of explosives are still present in the inlet system even tens of minutes after the vapors of certain explosives have been introduced into the sample inlet line. This is the main drawback of the current system. Another problem is described in Wolfkoff (1995) Volatile Organic Compounds Sources, Measurements, Emissions, and the Impact on Indoor Air Quality. Indoor Air 5, 5-73], it is the reliability of internal laboratory control and fluctuations in the laboratory due to artifacts.

Explosives behave very similarly to common (semi-)volatile organic compounds (VOCs), so the same sampling problem applies. There are three main options when sampling VOCs:

(a) application of a medium that physically or chemically binds the target compound,

(b) application of storage devices such as canisters,

(c) Collection through tube.

The first two methods result in discrete analyzes that provide snapshots in time or average composition over a period of time, both requiring transfer of the material to the analytical instrument. Target compounds can be detected in real time by using a tube directly connected to an analytical instrument capable of performing continuous analysis.

The choice of tube size and material is essential for a successful and reliable analysis with little or no memory effect. The memory effect occurs when the sampled material adheres to the wall material of the tube and is later released into the sample stream due to a physical force or chemical reaction, which is one of the main causes of false positive values in air monitoring. The approach to detecting explosives has not changed over the past 10 years since its introduction in the 1990s, see Yinon J. and Zitrin S. (1996) Modern Methods and Applications in Analysis of Explosives. John Wiley & Sons, 316 pp. It is described in https://books.google.com/books?isbn=0471965626 ] that "in the mobility detector, an air sample was aspirated into the ion source through a PTFE-lined heated tube." In general, it is believed that heavy molecules are adsorbed on the conveying tube for a sampling line length of several feet or more. Most of the tests are conducted in indoor conditions with tubes of several feet. To solve this sampling problem, some approaches attempt to first perform a modification of the material into an ionic phase and then transport the ions over a distance. The maximum reported length of these ion transport tubes is still less than 10 feet (Cotte-Rodriguez and Cooks (2006) Non-proximate detection of explosives and chemical warfare agent simulants by desorption electrospray ionization mass spectrometry. Chem. Commun. 28 , 2968-2970).

Mass spectroscopy was chosen as the analytical technique for detecting trace VOCs. Typically, an air sample is ionized and then introduced into a mass differentiation spectrometer using a magnetic field. The ionization method, when analyzed by this method, has the greatest impact on the integrity of any given material. The so-called chemical ionization technique is designed to prevent molecules from completely fragmenting while being charged. One of these techniques involves a Proton-Transfer Reaction (PTR), which creates a Proton Transfer Reaction Mass Spectrometry (PTR-MS) method along with a mass spectrometer (MS). As described in patents DE 1995149144 and WO 2014/053540 A1 and the references cited therein, PTR-MS uses water or other small ions to generate primary ions, which in turn proton target substances in air samples. Get angry. One of the main advantages of PTR-MS over other soft-ionization techniques is that no carrier gas is required. Remote and independent operation is much more effective without a gas cylinder or other carrier gas source. Because many explosives are less volatile, it is commonly stated that collecting these explosives in air sampling systems requires heating lines for effective transport and high voltages for ionization. Mayew C., et al. (2010) Applications of proton transfer reaction time-of-flight mass spectrometry for the sensitive and rapid real-time detection of solid high explosives. Int. J. Mass Spec. 289, 58-63] states: For general explosive detection it is important to note the following: "For the low vapor pressure associated with solid explosives, an additional procedure has been adopted to obtain a higher VOC concentration. This includes It involved designing and utilizing a simple pre-concentrator and thermal desorption system”. Also, "The sample inlet lines were all about 1 m long and the sample was delivered to the PTR inlet system. It was heated and held at 120° C. to minimize surface adsorption". Different studies have been published in Jurschik S., et al. (2010) Proton transfer reaction mass spectrometry for the sensitive and rapid real-time detection of solid high explosives in air and water, Anal Bioanal Chem. 398, 2813-2828], which used somewhat similar conditions as follows: "for gas phase samples, the analyte has an adjustable flow rate of 50 to 1,000 sccm and an adjustable temperature of 40° C. to 150° C. The furnace is introduced through the gas inlet system". However, heating of the tube and associated voltage in the ionization chamber causes fragmentation of the TATP molecules. TATP initiates fragmentation at temperatures above 145°C (see Matyas R. and Pachman J. (2016) Primary explosives. Springer, 360 pages), which means that inflow systems of their kind cause problems for this target Make it.

In view of the foregoing, it is clear that there is an important need for an effective method and associated apparatus for rapidly and accurately monitoring air samples for the presence of TATP, and the present invention satisfies this need.

It is an object of the present invention to provide a method and apparatus for continuous monitoring of TATP using mass spectrometry.

Another object of the present invention is to provide such a system that is portable and configured to be used as a security device in various remote locations for a long period of time or used in stadiums and stadiums during events.

Another object of the present invention is to provide such a system that can be mounted on vehicles and drones and can perform tests on samples of vehicles or drones.

Another object of the present invention is to provide a method and apparatus for real-time or near real-time monitoring of TATP.

Another object of the present invention is to use specific electronic conditions for the chemical ionization approach to such spectrometer monitoring.

Another object of the present invention is to use specific electronic conditions for the chemical ionization approach to such spectrometer monitoring.

Another object of the present invention is to provide a PTR-MS system that provides chemical ionization in which molecules are charged in an environment in which primary ions can be used for ionization of molecules.

Another object of the present invention is to use an inlet tube to deliver the sample to the ionization chamber.

Another object of the present invention is to withstand excessive fragmentation by controlling the energy input within the ionization chamber.

Another object of the present invention is to provide a system capable of performing mass spectrometer monitoring by simultaneously testing two or more samples.

Another object of the present invention is to use PTR-MS to maximize protons of ions to produce improved results from mass spectrometers that accommodate them.

Another object of the present invention is to provide a method and associated apparatus that allows simultaneous analysis of very different molecules.

Another object of the present invention is to provide a system that further analyzes a segment of the original sample and provides a validation cycle to reduce false positives in order to verify the result.

Another object of the invention is to provide such a system that does not require the use of a carrier gas.

Another object of the present invention is to reduce false responses due to no memory effect in the sampling pipe.

Another object of the present invention is to provide a sensitive analysis of TATP without any significant loss of the sample or modification to the sample during transport from the source to introduction to the processing device.

Another object of the present invention is to provide a system using the simultaneous chemical ionization and analysis of unstable compounds requiring low energy conditions and compounds requiring higher energy to ionize effectively.

These and other objects of the invention will be more fully understood from the following detailed description of the invention with reference to the examples appended herein.

The analysis performed by PTR-MS depends on several parameters. The sampled air enters the ionization chamber, sometimes referred to as the reaction chamber or drift tube. The air is then mixed with a stream of primary hydronium ions and, based on the proton affinity of the particular compound, is protonated or not. The portion of air that is protonated by the proton-transfer reaction enters the mass spectrometer, is separated and identified by mass. The remaining air that is not protonated is released by the device. The main parameters of this analysis are the amount of air entering the instrument over a period of time (the standard setting is 200 standard cubic centimeters/minute (sccm)), the temperature of the ionization chamber, and the sample inlet temperature (which is typically 5°C lower than the reaction chamber. Set), the vacuum in the ionization chamber and the voltage applied to the ionization chamber. The temperature, vacuum, and voltage control the reaction rate of the transfer reaction, causing more or less material to be protonated, which directly affects the detection limit of the assay. Fragmentation of the molecule creates a very specific particle pattern in the mass spectrometer for each compound. However, both indoors and outdoors, in mixtures of large amounts of compounds, such as unfiltered air, fragmentation results in a tremendous increase in small parts that often overlap each other or otherwise indistinguish from their origin. Hence, being able to identify the complete, unmixed molecule is the key to detecting the ultra-trace concentrations of target molecules in an air sample.

In addition, TATP is very fragile and can be protonated with minimal energy impact without causing substantial fragmentation. A fragment of TATP is, in particular, acetone, a compound that is generally present in a much greater concentration than TATP. Applying a minimum voltage to the reaction chamber can prevent too much fragmentation, but the side effect of applying a low voltage to the reaction chamber is that a large amount of water clusters are formed from hydronium ions. This leaves a very reduced amount of hydronium ions to protonate other molecules. Water clusters can also trigger chemical reactions with target molecules, further weakening the signal of the compound.

The best electrical setup of PTR-MS when detecting explosives is described in Suzer P., et al. (2013), Applications of switching reagent ions in proton transfer reaction mass spectrometric instruments for the improved selectivity of explosive compounds, Int. J Mass Spec 354-355, 123-128], the standard settings are rather well defined ("Most users of PTR-MS have approximately 110 Td to 140 Td (1 Td = 10 to 17 V cm2). ) Of the fixed reduced electric field E/N (the ratio of the electric field strength E to the buffer gas number density N in the ionization chamber), a value in this range, the minimum formation of protonated water clusters, the protonated parent It is considered a good compromise between the limited fragmentation of the parent species and the appropriate reaction time, thereby maximizing the sensitivity of compound detection. Using hydronium ions as proton donors, protonated water clusters [H ₃ O ⁺ _x (H ₂ O) _n (n≥1)], due to the formation of (depending on humidity) for E/N values well below 90 Td, the signal strength drops sharply, limiting the usable E/N values .").

Using current instrumentation equipment, see Sulzer P., et al. (2013) Applications of switching reagent ions in proton transfer reaction mass spectrometric instruments for the improved selectivity of explosive compounds. Int. As specified in J Mass Spec 354-355, 123-128, settings for detecting TATP or other explosives can be optimized and switched quickly. However, this results in loss of information over 50% of the sampling time, which can have a devastating impact if identification of the explosive-containing source passing through the sampling inlet is not possible.

1A and 1B show the sampling configurations for outer tubes of different diameters, respectively, that deliver the tested sample to an ionization chamber (also known as a reaction chamber or drift tube).
2 is a schematic diagram of a dual inlet embodiment of the present invention.
3A is a combined schematic block diagram of the verification module of the present invention.
3b schematically shows the valve 42 in the normal mode.
Figure 3c schematically shows the valve 42 in the verify mode.
Figure 3d schematically shows the valve in storage mode.
4 is a block diagram of a verification module with two divided air pockets.
5 shows a plot showing the optimum voltage for ionizing TATP when compared to RDX and TNT.
FIG. 6 shows a plot of the TATP reaction of 0.5 g in an air volume equivalent to an automobile at m/z 223 (complete molecule) and m/z 91 (fragment).
7A shows the mass spectrum for m/z = 223 for an instant.
7B shows the mass spectrum for m/z = 91 during the same time as in FIG. 7A.
7C shows the rapid onset and decay of the signal response to TATP sampling.
8 is a plot showing sample delay due to varying air flow when using a 3/8 inch outer diameter 100 foot tube made of PFA.

Justice

As used herein, the following abbreviations will have the following meanings.

TATP: triacetone tripperoxide (3,3,6,6,9,9-hexamethyl-1,2,4,5,7,8-hexoxonane; CAS# 17088-37-8)

TNT: 2,4,6-trinitrotoluene

VOC: Volatile Organic Compound

PTR: proton-transfer reaction

MS: mass spectrometer

PTR-MS: proton-transfer reaction mass spectrometry

PTR-Hydra: PTR-MS instrument with multiple ionization chambers

E/N: ratio of electric field strength to density of the number of buffer gases in the ionization chamber

PFA: perfluoroalkoxy alkanes

PEEK: polyether ether ketone

RDX: 1,3,5-trinitro-1,3,5-triazine

GC-MS: gas chromatography-mass spectrometry

TDU tube: Thermal desorption unit tube

m/z: ratio of mass to number of ionic charges

Sift means “selected ion flow tube”, a chemical ionization technique similar to PTR, and the physics of the transfer reaction in the ionization chamber are the same.

The method and apparatus of the present invention enables continuous and parallel monitoring of samples for TATP through protonation by chemical ionization. Chemical ionization uses primary ions to induce a charge transfer reaction, which produces an ionized target molecule. There is minimal energy impact in this transfer reaction. This means that the material is less fragmented when it reaches the mass spectrometer.

The device is capable of producing several ion streams from the same air sample under different temperature, pressure and voltage conditions within the ionization chamber. The device also makes it possible to identify these multiple ion streams in parallel within a single mass spectrometer that produces a single mass spectrum for the original air sample. The verification loop in the device can immediately verify a positive identification using a subpart of the original air sample used for the original identification.

The present invention consists of several aspects that provide a wide variety of measurement systems for TATP while being able to reduce the likelihood of false positives, which consists of:

(a) Use of sampling tubes of specific material, diameter and length capable of detecting TATP and other explosives.

(b) Specific settings of pressure, temperature and voltage in the ionization chamber for optimal TATP detection.

(c) Design of a device based on chemical ionization mass spectroscopy to perform continuous monitoring of explosives in parallel and in real time for substances with different proton-transfer reaction conditions (e.g., TATP and TNT during analysis and verification It requires a different setup for this, this approach reduces the amount of false negative results).

(d) Design of a plug-in verification module that can be introduced into any analytical air monitoring device to verify positive identification using partial samples of the original sample material (in particular, this module is a PTR- Can be inserted into Hydra to directly verify TATP or other explosives to reduce false positive rates).

Description of preferred embodiments

1. The term “sampling tube” or “sampling tube” has generally been used for items less than about 200 feet to take samples from a source. The terms "inlet pipe" or "inlet pipe" have generally been used for items of about 10 feet or less that take a sample at the end of a sampling pipe or pipe and deliver it for processing. The term “transfer tube” will be used to refer to a combination of “sampling tube” and “inlet tube”.

2. The word "ionization chamber" is mainly used in place of the words "reaction chamber" and "drift tube", receiving a sample of air from the inlet tube or inlet piping and mixing it with the primary ion stream to create an ionized target species. It is used interchangeably to refer to the part of the system to be used.

Certain piping provides an ideal environment for TATP sampling under field conditions. It has been found that the most suitable tubing material for sampling and inlet piping to deliver the sample to the ionization chamber is an inert plastic material such as perfluoroalkoxy alkanes (PFA) or polyether-ether-ketones (PEEK). The tube may be made entirely of PFA or PEEK or may be made of a PFA-lined or PEEK-lined tube made of other mantle material, such as braided steel, silicone outer cover or equivalents thereof. For the identification of TATP, the best and most reproducible identification is an outer diameter of ¼" to ½" that is about 5 to 200 feet in length, preferably about 100 to 200 feet, and most preferably about 5 to 100 feet ( It has been found to use a feed pipe with OD) PFA tubing and 1/16" OD PEEK inlet tubing. This method involves using a sampling pump to draw air through the tubing. Figure 1A shows the pump 2 ) Pulls the tube-delivered sample from the sampling point to the three-way connection 6. The vacuum system of the device 4 then draws a portion of it through the inlet pipe to the device. The piping specifications are listed on the left side of the valve 6. The 1/16" PEEK piping in the machine is factory setting and is optimized for example 1/8" piping.

Another sampling setup is to use 1/8" OD PFA tubing about 200 feet or less in length without an auxiliary pump, and using 500 sccm or less establishes the flow of the sample using the internal vacuum system of the analytical instrument to draw the sample. The ionization chamber is preferably heated internally to provide improved control of the rate and efficiency of the proton-transfer reaction In general, the higher the heating temperature the faster the reaction, but fragile molecules such as PTAT will become fragmented. In addition, higher temperatures result in discharging of the molecules striking the side of the ionization chamber, leading to losses in the mass spectrometer processing, Figure 1B shows the sample from the sampling pipe through the connection 14 and the PEEK inlet pipe. The above setup is shown in a system equipped with a receiving device 12. The present inventors do not require the desired heating of the sampling tube with an adequate sampling air flow, but the signal strength is reduced when the sampling temperature is as low as about 36°F or 20°C. Was confirmed to decrease by about 50%.

It has been found that the optimum air flow through the sampling piping to detect TATP is about 0.1 to 25 liters per minute, preferably about 3 to 7 liters per minute. This is an optimal condition for reducing the signal delay time while limiting the dilution of the signal due to the difference in air flow in the sampling pipe and the inlet pipe.

The inventors have found that the signal response of PTR-MS to TATP can be optimized by varying the voltage and operating temperature in the ionization chamber. PTR-MS is often referred to as PTR-TOF-MS, which is a time-of-flight (TOF) mass spectrometer (in microseconds) as opposed to a quadruple instrument (measurement is performed in minutes). It is also emphasized to refer to a measurement). The voltage is applied at about 150 to 650V, preferably about 200 to 250V, the pressure is about 2.0 to 4.0 mbar, preferably about 2.1 to 2.3 mbar, the operating temperature is about 70 to 120°C, preferably about 80 to It should be set to 100℃. During the evaluation period, the IONICON PTR-TOF-4000 and Ionicon PTR-TOF-1000ultra instruments were used, and as confirmed, it appears to be generally applicable to systems requiring ionization of vapors for identification. Briefly, it is necessary to optimize its operating parameters in relation to the maximum ion influx entering the mass spectrometer for a given amount of TATP in front of the inlet tube. The PTR-Hydra concept can be used by using components from equivalent devices such as TOFWERK Vocus devices or SYFT Voice200 devices.

In terms of ions counted per mass of material, the best results were obtained using a PFA 100 ft 3/8" tube with a wall thickness of 0.065" and an air flow setting of 10 L/min. The PTR-MS inlet flow rate was set to 200 sccm and the inlet temperature was set 5° C. lower than the ionization chamber temperature. In terms of ionization chamber voltage and ionization chamber temperature for TATP, it has been found that the optimum electronic settings are 175 to 275 V and the temperature is 80 to 120° C., preferably 215 to 235 V and a temperature of 95 to 105° C.

The inventors have confirmed that the optimum voltage and temperature are as follows under the same setting of the length and diameter of the external sampling tube and the pressure of the ionization chamber in the PTR-MS:

(a) In the case of TNT, a temperature of 600 to 800V, preferably 750 to 800V, and 100 to 140°C, preferably 120 to 130°C.

(b) In the case of PETN and RDX, a temperature of 300 to 500V, preferably 375 to 425V, and 80 to 120°C, preferably 90 to 110°C.

For the modified PTR-MS design and PTR-Hydra-MS, the conditions and required electrical settings for identification of (a) TATP and (b) other explosives and/or drugs are completely different. The setup for TATP promotes the formation of water clusters, preventing protonation of other substances, which greatly increases the detection limit. One way to deal with the need for different settings for TATP and other explosives is described in the literature by Sulzer P., et al. (2013), where a series of devices is switched by switching the settings at intervals of 5 to 10 seconds. Eliminate the monitoring aspect. If the signal duration is in the range of 1 to 5 seconds, the probability of missing occurrence is 50%.

Another solution is to perform continuous analysis for TATP and other compounds, installing two or more PTR-MS instruments synchronized and fed in the same sampling tube. However, to reduce installation space, cost and synchronization issues, an integrated approach would be useful.

The proposed solution is a multi-entry PTR-MS called PTR-Hydra-MS. The design shown in Figure 2 represents the option of a dual inlet system. The design can be extended to a minimum of six integrated ionization chambers if necessary. The limitation is primarily the size of the ionization chamber and the geometry due to the interference of the electric field from each ionization chamber to the next. This embodiment provides the ability to detect a different range of compounds for the use of multiple ionization chambers, thereby allowing different compounds to be analyzed simultaneously.

The inlet pipe 20 is made of a material such as PEEK, but a material such as PFA or equivalent material may be used. The material should be inert to the compound of interest to prevent fragmentation or retention of the signal. The diameter must comply with the specific equipment requirements for optimal air flow into the system. The sample is then divided into equal parts 22 entering multiple inlet lines 24 of the same material, diameter and length.

The individual ion sources 23, 25 and the ionization chambers 26, 27 are preferably identical to each other in terms of material of construction, dimensions and performance. This point is important in minimizing the difference in transfer of the ionized species to the mass spectrometer. Although different electrical settings within the ionization chamber can make the speed of ions directed to the mass spectrometer different, this difference is several times shorter than that of the mass spectrometer's signal binning. However, different lengths of the ionization chambers may misalign the timing of the ions received by the mass spectrometer, resulting in erroneous identification of compounds within a particular air sample. The ionization of air molecules within the ionization chambers 26 and 27 takes place based on specific reactions to various types of ionization methods. For example, a proton-transfer reaction or a charge transfer reaction may be a driver. The resulting streams of ionized species 28 and 29 are then combined into one stream using multiple inlet ion funnels 36 as described in US Pat. No. 6,979,816 B2. The combined ion stream is then delivered to an identification device based on the mass spectrometer 32. Ion delivery may or may not involve additional ion stream focusing devices such as multi-poles or ion funnels. A portion of the air that is not ionized exits the ionization chamber at outlet 34.

The individual ionization chambers 26 and 27 are configured identically, but they can be operated independently with different electrical settings and different reactive ions. As disclosed in patent publication WO2014/053540 A1, applying different primary ions to the ionization chamber may be advantageous for the ionization of the target compound.

The main parameters that can be set independently are internal pressure, temperature and applied voltage. One can be run with optimized conditions specific to one compound or class of compounds (T1, P1, V1 in Fig. 2), and the other is run with optimized conditions (T2, P2, V2) for the other compound. This ensures that any given air package exiting the sampling line is ionized in several ways with conditions optimized for various targets.

For example, one of the chambers may be set to optimal conditions for identifying TATP and the other chamber may be set for optimal identification of other explosives. The setting for TATP is unique within the PTR-MS application as far as the presence of water clusters is taken into account, making this setting somewhat disadvantageous for other analytes. On the other hand, settings to identify other explosives, such as TNT, cause about 40% loss in the signal response of _TATP (ideal conditions V _TATP = 225V, T _TATP = 100°C; V _TNT = 775V, T _TNT = 125°C ).

A preferred embodiment of this setup is to use two or more ionization chambers in a setup equivalent to PTR-MS. The ionization chambers 26 and 27 can be constructed as an assembly of glass tubes or metal rings with RF induction. The upper limit of the number of ionization chambers is limited by geometrical problems, electric field interference and the capacity of the mass spectrometer.

An alternative embodiment may be a setup equipped with two or more ionization chambers or equivalent chemical ionization chambers configured as a selected ion flow tube (SIFT). PTR aims to produce a single ion stream of hydronium or other specific negative ions, such as O+ or NO+, while SIFT produces a mixture of ions and all their compounds resulting from ionizing the surrounding air and then It aims to filter this excess ions into a single ion stream and then use them in an ionization chamber to produce secondary ions such as PTR. The advantage of the SIFT approach is that it is possible to quickly switch between the reacting ions, and the disadvantage is that filtering of the ions greatly reduces the total ion flow, worsening the sensitivity. In the case of the present invention, the present inventors must include and use this technique, since the main competitor to PTR devices in the commercial market is configured as SIFT devices. Also, as in PTR devices, a verification loop can be easily included in SIFT devices.

A validation module has been developed to reduce false positive identification (i.e., positive identification showing positive results despite lack of suitable material in the sample). This module is added to the common inlet system in the appliance as shown in Fig. 2 and replaces the direct inlet line 24. 3A-3D, the module operates in three settings: "Standard" mode for normal analysis tasks (FIG. 3B); "Verify" mode for re-irradiating air samples with the same or different settings of the ionization chamber (Figure 3c); “Save” mode for storing air samples for analysis in later steps using another instrument (Figure 3D). Storage can be carried out, for example, in a storage device selected from the group consisting of an air canister, a bag and a detachable tube. The air flow is driven by a vacuum applied from the device's internal vacuum pump 46. A portion of the air stream 46 is then introduced into the ionization chamber 44. The other part is kept in the verification loop 48 so that the first fraction can be analyzed and the second fraction still available in the instrument. For example, if TATP is identified as positive, a second fraction can be sent back to the ionization chamber 44 for verification. Details of the invention are shown in FIG. 3 and described in detail later. The plug-in setup consists of the common parts of a chemical ionization mass spectrometer: an ion source, an ionization chamber, a guide for the ions, and a mass spectrometer to identify the mass of the ions. The inlet system generally includes an inlet with a specific air flow, depending on the applied vacuum. A portion of that air stream is then introduced into the ionization chamber. This inlet is the starting point of the invention shown in Figs. 3A-3D.

As shown in Fig. 3A, the inlet line 41 is divided into two lines of the same material but different lengths, both of which are connected to the same vacuum pump. The valve 42 on the line may transfer the air sample from the secondary line to the primary line. The primary line 43 is a line permanently connected to the ionization chamber 44. The secondary line 50 is the line that needs to switch the valve 42 to connect to the ionization chamber 44. In the description below, the secondary line is referred to as a “sample loop”. For a detailed description of the operation of the verification module, refer to FIGS. 3 and 4.

3A, 3B and 4, the sample from the sampling inlet line 41 reaches the valve at the splitting point 40, and then one sample portion A is 1 through the multi-line valve 42. It enters the inlet line 43 through the car line and enters the reaction chamber 44. Ionized species from this sample are transferred to a mass spectrometer 45 for analysis. The non-ionized portion of the portion A is transferred to the vacuum pump 46 through the outlet 47. Meanwhile, the sample portion B moves through the secondary line 48. The portion B is drawn into the sample loop 48 by the same vacuum from the vacuum pump 46. The loop 48 is preferably made of the same inert material as the sample inlet 41, the primary line 43 and the transfer line 50, and the residence time of the sample portion B in the sample loop 48 Depending on the type of mass spectrometer 45 and its response time, it has a length of about 2 to 5 seconds or more. Under normal operation, the part B will then be pulled with the same vacuum pump 46 as part A. For optimal results, the material for the sample loop 48 needs to be minimal or have no fragmentation and chromatographic effects on the target material.

In the case of the positive ID of the sample portion (A) measured by the mass spectrometer 45, as shown in Fig. 3c, the valve 42 is switched to the "verification mode" and the portion B is connected to the valve 42. Connect. Portion B is then transferred via inlet line 43 to ionization chamber 44, ionized and then analyzed in mass spectrometer 45 for confirmation of positive ID. Alternatively, the valve 42 can be turned to the storage position shown in FIG. 3D.

3A and 4, and referring to the verification module provided to verify the result, the index represents a specific time, for example, A ₁ and B ₁ are two divided at time t = 1 It is an air pocket. A ₀ B ₀ is the original air sample introduced into the sampling line.

The main advantage of this arrangement is that in case of positive ID of bolus emission, the same original air package can be used for reanalysis. This allows the use of optimized conditions for potentially positively identified substances by changing the electrical settings of the reaction chamber and/or mass spectrometer. If optimal conditions have already been applied, this serves as a true validation to reduce false positive IDs.

For example, the positive ID of TATP using optimized conditions produces specific peak heights of m/z 223 and 91, respectively. When verifying TATP, the voltage can be increased, which will decrease the amount of 223 and increase the amount of 91 to a predetermined amount according to the fragmentation pattern of TATP. In the case of positive validation of the TNT signal, the ionization chamber voltage was increased and reference [Sulzer P., et al. (2012) Proton Transfer Reaction Mass Spectrometry and the Unambiguous Real-Time Detection of 2,4,6 Trinitrotoluene. Anal. Chem. 84, 4161-4166] 21, the signal at m/z 228 increases.

A preferred embodiment of this module is in an instrument based on a proton-transfer reaction mass spectrometer (PTR-TOF-MS), a selected ion flow tube mass spectrometer (SIFT-MS) or any more general chemical ionization mass spectrometer. These continuous air monitoring devices have the greatest advantage in terms of their ability to verify bolus emissions within seconds.

Alternative embodiments of this part of the invention include any near-real-time air monitoring device, including gas chromatography mass spectrometry (GC-MS), cavity ring down spectrometry, or equivalents thereof. will be.

An alternative embodiment of this part of the invention is that the connection between the primary and secondary sample lines is a transfer line to an air storage device such as a Summa canister or a thermal desorption unit tube (TDU-tube). It could be a replacement. This kind of setup allows long-term storage of materials identified as positive for validation by secondary techniques. In some cases, ongoing monitoring analysis is not considered legally defensible and should be verified by an accredited method such as GC-MS. Storage of air samples with positive identification ability based on continuous monitoring techniques greatly improves the monitoring efficiency (see Fig. 3D). Examples include environmental areas such as brownfield improvement sites, law enforcement areas such as vehicle or human monitoring for drugs or explosives, or research areas for capturing bolus emissions in internal combustion engine research.

Figure 5 is a direct comparison of the effect of a specific set of conditions in the ionization chamber on the amount of ionized molecules. "Normalized Signal" shows the counts per second measured in a mass spectrometer, normalized to the maximum count amount of each compound. In this graph, temperature and pressure are fixed at 80℃ and 2.2mbar, respectively, and voltage V is a variable. The best voltage setting for TATP at 200-250V does not produce TNT or RDX in the ionized molecules, so no such compounds are detected. At the voltage best suited for RDX at 400V, TNT produces only about 15% of its maximum intensity, and can thus lead to false negative results. In addition, TNT tends to ionize much better at higher temperatures than thermal decomposition at 145°C.

For reproducible identification of TATP using hydronium as the ionizing agent, both masses m/z = 223 and 91 are the best choices. There are no other compounds likely to be in the environment with a parent mass near 223 and a fragmentation pattern containing 91. One of the few compounds that are very prevalent in environments where m/z = 223 is diethylphthalate and the other is hexamethylcyclotrisiloxane. The first one is semi-volatile with low vapor pressure, but can appear at high concentration locations if found (however, it does not essentially show fragmentation, especially at m/z = 91). The second substance can be found in household products and is neither fragmented at m/z 91. When preparing TATP, when an ammonium-containing substance or ammonium is used as an ionizing agent instead of hydronium, the mass m/z = 240 is the mass of the unfragmented molecule. This can be considered when working with materials of unknown origin.

Other fragments with prominent peaks such as m/z = 59, 61, 43, 89, 74, 75 (with decreasing intensity) are indistinguishable from common VOCs in air, such as acetone, or from water clusters. Is similar/overlapping with it.

Example

This example includes an example setup with an open TATP canister of 0.5 g for an air volume equal to the volume of a small car. The ambient temperature was in the low 40°F range and the air volume was heated at 72°F for 5 minutes in the presence of an open canister. This scenario is designed to mimic an inspection situation in which the driver opens the side window and the end of a 100 foot 3/8" sampling tube camouflaged within the guard's jacket sleeve is directed towards the atmosphere. The end of the tube is approximately at the opening representing the open window. It was at a distance of 6 inches. The graph shown in Fig. 6 shows the response of a parent mass of 223 and a primary fragment mass reading of 91, denoted by reference numerals 60 and 62, respectively. The above measurements follow the TAPT analysis described herein above. Was carried out using optimized electronic conditions.

The following example includes sensing TATP at a distance of 6 inches from the tube end.

This case shows the response speed and specificity of the signal at mass 223. 7A shows the mass spectrum for a specific moment. This shows a narrow peak at m/z = 223. 7B shows a graph for the same time period at mass m/z = 91. The peak is significantly larger than the case of m/z=223. The system will provide a positive reading for the presence of TAPT when the analysis results show both a reading of 223 for the primary molecule and a reading of 91 for the primary fragment. Both ions must be present to conclude that TAPT is present in the sample. When the mass m/z 223 is insufficient and m/z 91 is high, it is advantageous to evaluate that there is a mass m/z 240 representing the complete molecule with ammonium substitution. The amount of TATP present is correlated with the amount of counts/second at a given m/z value. This is directly related to the size of the peak as shown in FIG. 6. The count/second produces a peak spectrum as shown in Figs. 7A and 7B.

The first reading of the mass spectrometer is counts/second/mass. This is the result of conversion from the measured actual parameters, which is the period between the pulse set at the start of the mass spectrometer and the time the ions arrive at the detector at the end of the spectrometer reading. The narrower the peak, the more precise the spectrometer works, and the area under the peak is used for quantitative analysis.

In Fig. 7c two masses m/z = 223 and 91 are plotted over time. This shows that the onset of the signal is basically within 1-2 seconds of no memory effect, and the signal falls to the background within the same time frame as the start. The lack of memory effect using PFA tubes is essential to reduce false positive responses in security applications.

The graph in Figure 8 shows the relationship between airflow and signal delay in the sampling tube when using a 100ft long 3/8" OD sampling tube to introduce air samples for PTR-MS monitoring for TATP. With reduced airflow The resulting sample delay can be significant at inlet rates of less than 1 L/min, which suggests that using the PTR-MS's internal vacuum system to reduce the sample rate can increase the delay in signal response to potential threats by up to ½ min. it means.

While certain embodiments of the invention have been previously described for purposes of illustration, it will be apparent to those skilled in the art that various modifications of details may be made without departing from the invention as defined in the appended claims.

Claims (79)

As a method of monitoring a sample for TATP,
Providing a delivery tube for delivering the sample to the device,
Providing the device with an ionization chamber configured to receive the sample from the delivery tube,
Transfer the sample to the ionization chamber,
Placing the sample under a proton-transfer reaction to generate ions that protonate the target substance in the sample,
To determine the m/z value, the protonated ions are transferred to a mass spectrometer,
If the mass spectrometer provides a reading of one of 223 and 240 for the parent ion and a reading of 91 for the fragment, determining that TATP is present in the sample.
How to include. The method of claim 1,
The method, wherein the sample is air. The method of claim 1,
Wherein the delivery tube has a sampling tube that is about 5 to 200 feet in length. The method of claim 3,
The flow rate of the sample through the sampling tube is about 0.1 to 25 liters per minute. The method of claim 3,
The flow rate of the sample through the delivery tube is about 0.1 to 0.5 liters per minute. The method of claim 1,
The method comprises using a plurality of said ionization chambers each containing an equal fraction of said sample,
Wherein the protonated ions from each of the ionization chambers are delivered to the mass spectrometer. The method of claim 6,
A method comprising using two said ionization chambers. The method of claim 6,
A method comprising using a multiple inlet ion funnel to combine ions before the ions enter the mass spectrometer. The method of claim 1,
And heating the ionization chamber. The method of claim 9,
And heating the ionization chamber to about 80°C to 120°C. The method of claim 2,
And discharging non-protonated air from the ionization chamber to the atmosphere. The method of claim 1,
And performing the method continuously during the monitoring. The method of claim 1,
And performing the monitoring on a real time basis. The method of claim 1,
A method comprising using chemical ionization to reduce fragmentation of molecules during ionization. The method of claim 1,
Processing the fragment of the sample formed during the protonation of the sample by the mass spectrometer,
Using the output of the mass spectrometer from the fragment to identify the sample
How to include that. The method of claim 15,
Determining that TAPT is present in the sample if the mass spectrometer provides a reading of 223 for the parent ion and 91 for the parent fragment. The method of claim 15,
Determining that TAPT is present in the sample if the mass spectrometer provides a reading of 240 for the parent ion and a reading of 91 for the parent fragment. The method of claim 1,
Using a validation cycle to process the second fraction of the sample,
To determine if the mass spectrometer produces the same results as produced when processing the first fraction of the sample.
How to include that. The method of claim 3,
Wherein the sampling tube has an outer diameter of about ¼ to ½ inches. The method of claim 1,
Wherein the sampling tube is made of an inert material. The method of claim 20,
Wherein the delivery tube is made of a material selected from the group consisting of perfluoroalkoxy and polyether-ether-ketone. The method of claim 1,
The method, wherein the ionization chamber is operated below 120°C. The method of claim 8,
Wherein the multiple inlet ion funnel is selected from the group consisting of multiple metal rings, multiple rings of polyether ketones, and glass tubes with an induced RF field. The method of claim 1,
Not heating the delivery tube. The method of claim 3,
Wherein the delivery tube has an inlet tube having an outer diameter of about 1/16 to 1/8 inch. The method of claim 1,
A method comprising using a vacuum pump to provide the sample to the ionization chamber. The method of claim 1,
And using suction from the ionization chamber to provide the sample to the ionization chamber. The method of claim 18,
And using the verification cycle when the mass spectrometer provides a positive output indicating the presence of TAPT. The method of claim 1,
A method comprising using the method to monitor a sample for acetone peroxide. The method of claim 1,
And subjecting the sample within the ionization chamber to a chemical ionization process. The method of claim 1,
Wherein the delivery tube has a sampling tube that is about 100 to 200 feet in length. The method of claim 3,
The method, wherein the delivery tube is internally coated. The method of claim 3,
Wherein the delivery tube is made of an inert material. The method of claim 4,
The flow rate of the sample through the delivery tube is about 7 to 10 liters per minute. The method of claim 3,
Wherein the delivery tube has a sampling tube that is about 100 to 200 feet in length. The method of claim 13,
Performing said monitoring in microsecond to minute increments between about 0.8 and 1.2 seconds. The method of claim 6,
A method comprising processing said sample for a different compound in each said ionization chamber. The method of claim 7,
Wherein the protonated ions from each of the ionization chambers are delivered to the mass spectrometer. The method of claim 6,
And individually controlling the internal pressure, temperature and voltage for each of the ionization chambers. The method of claim 10,
Wherein the heating of the ionization chamber is heating to about 95°C to 105°C. The method of claim 1,
Wherein the ionization chamber is operated at a voltage of about 175-275 volts. The method of claim 41,
Wherein the ionization chamber is operated at a voltage of about 215-235 volts. The method of claim 1,
And using a pressure in the ionization chamber of about 2-4 mbar. The method of claim 43,
A method comprising using a pressure in the ionization chamber of about 2.1 to 2.3 mbar. The method of claim 18,
Separating the second sample from the delivery tube prior to introduction into the ionization chamber. The method of claim 18,
Storing the second fraction of the sample instead of using the verification cycle. The method of claim 46,
A method comprising performing said storage of said second fraction in a storage unit selected from the group consisting of air canisters, bags and desorption tubes. As a device for monitoring a sample for TATP,
Delivery tube for delivering samples,
An ionization chamber opeably associated with the delivery tube to receive and generate ions from the sample, the ionization chamber configured to place the sample under chemical ionization to protonate a target substance in the sample,
As a mass spectrometer to receive protonated ions from the ionization chamber and to determine the m/z for the sample, the m/z reading of one of 223 and 240 and a fragment value of 91 when TATP is present in the sample. Mass spectrometer configured to provide
Device comprising a. The method of claim 48,
The apparatus is configured to process a sample that is air. The method of claim 48,
Wherein the delivery tube has a sampling tube that is about 100 to 200 feet in length. The method of claim 48,
The device has a plurality of the ionizers each receiving an equal fraction of the sample and generating ions therefrom,
Wherein the ionizer is configured to protonate the ions from each of the ionizers and transfer them to the mass spectrometer. The method of claim 51,
Wherein the device has two of the ionization chambers. The method of claim 51,
Multiple inlet ion funnel for combining ions from each of the ionization chambers before ions enter the mass spectrometer
Device comprising a. The method of claim 49,
Wherein the ionization chamber is configured to release non-protonated air into the atmosphere. The method of claim 48,
The device is configured to perform continuously during the monitoring. The method of claim 48,
And the device is configured to provide real-time monitoring. The method of claim 48,
Wherein the delivery tube has a sampling tube that is about 5 to 200 feet in length. The method of claim 48,
Verification unit for processing other fractions of the sample to confirm the accuracy of the results obtained from the original fraction of the sample
Device comprising a. The method of claim 57,
Wherein the delivery tube is made of an inert material. The method of claim 59,
Wherein the delivery tube is made of a material selected from the group consisting of perfluoroalkoxy and polyether-ether-ketone. The method of claim 59,
Wherein the sampling tube has an outer diameter of about 1/4 to 1/2 inch. The method of claim 48,
Wherein the delivery tube is configured to deliver the sample to the ionization chamber under the influence of a vacuum pump. The method of claim 51,
Wherein the ionization chamber is configured to place the sample under a chemical ionization process to protonate a target substance in the sample. The method of claim 48,
Wherein the delivery tube is internally coated. The method of claim 48,
Wherein the delivery tube is made of an inert material. The method of claim 65
Wherein the delivery tube is composed of a material selected from the group consisting of perfluoroalkoxy and polyether-ether-ketone. The method of claim 48,
The apparatus is configured to provide a sample flow rate of about 0.1 to 25 liters per minute. The method of claim 67,
The apparatus is configured to provide a sample flow rate of about 7 to 10 liters per minute. The method of claim 48,
Wherein the device is configured to release non-protonated air from the ionization chamber to the atmosphere. The method of claim 56,
Wherein the device is configured to perform the monitoring on a real-time basis in microsecond to minute increments of about 0.8 to 1.2 seconds. The method of claim 48,
Wherein the ionization chamber is composed of a material selected from the group consisting of multiple metal rings, multiple rings of polyether-ether-ketone and a glass tube with an induced RF field. The method of claim 51,
Wherein the ionization chamber has means for individually controlling an internal pressure, temperature and voltage for each of the ionization chambers. The method of claim 48,
The device is configured to heat the ionization chamber,
The apparatus is configured to heat the ionization chamber to about 80-120°C. The method of claim 73,
The apparatus is configured to provide an applied voltage of about 175-275 volts to the ionization chamber. The method of claim 48,
The apparatus is configured to use a vacuum system inside the ionization chamber to draw a sample into the ionization chamber without using a separate vacuum pump. The method of claim 48,
The device is configured to apply a vacuum of about 2 to 4 mbar within the ionization chamber. The method of claim 58,
The device having a storage unit for storing a fraction of the sample. The method of claim 77,
Wherein the storage unit is selected from the group consisting of an air canister, a bag and a detachable tube. The method of claim 61,
Wherein the delivery tube has an outer diameter of about 3/8 to 1/2 inch.

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